Many devices require an accurate reporting of the characteristics of a battery, capacitor, or related energy storage system (ESS) in order to recognize when additional charging is required. One technique of reporting the characteristics of an ESS involves the State of Charge (SOC), which represents the amount of electrical charge in the system. The problem with reporting the SOC as a characterization of the ESS is that it only gives a percentage of the energy available to the operator of the vehicle. Therefore, the SOC does not accurately represent the true capability or capacity of the ESS, and thus fails to account for the size, age, and recent operational history of the ESS. For example, the SOC may not account for the particular duty loads, driving patterns, and operational cycles undergone. The inaccuracies of a SOC characterization are magnified as it is incorporated into the control systems of hybrid and electric vehicles, which are configured to process only characterizations of the ESS in units of energy.
Accurate reporting of the state of the ESS is important to optimal vehicle operation. Impacted vehicle operations may include charging operation, extended electric range calculations, regenerative energy capture modes, gearing calibrations, and others. Inaccurate reporting of the state may be especially consequential when calculating the range of an electric vehicle, as it could result in a driver prematurely running out of motive power. Unfortunately, accurate reporting of the state of the ESS is hampered by the highly unpredictable duty loads that result from varied driving styles, behaviors, and conditions.
Accordingly, there remains a need for a way to accurately report available energy remaining in energy storage system used in a vehicle.